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  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K48/00—Medicinal preparations containing genetic material which is inserted into cells of the living body to treat genetic diseases; Gene therapy
  • A61K48/005—Medicinal preparations containing genetic material which is inserted into cells of the living body to treat genetic diseases; Gene therapy characterised by an aspect of the 'active' part of the composition delivered, i.e. the nucleic acid delivered
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
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• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P27/00—Drugs for disorders of the senses
  • A61P27/02—Ophthalmic agents
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  • C07—ORGANIC CHEMISTRY
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  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/46—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates
  • C07K14/47—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates from mammals
  • C07K14/4701—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from vertebrates from mammals not used
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  • C12N2750/00011—Details
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  • C12N2750/14111—Dependovirus, e.g. adenoassociated viruses
  • C12N2750/14141—Use of virus, viral particle or viral elements as a vector
  • C12N2750/14143—Use of virus, viral particle or viral elements as a vector viral genome or elements thereof as genetic vector

Definitions

• the invention relates to methods for treating a human subject who has X- linked Retinitis Pigmentosa (XLRP) or another ophthalmological condition due to a loss-of- function mutation in the gene encoding the retinitis pigmentosa GTPase regulator (RPGR) protein, the method comprising administering to the subject a nucleic acid comprising an adeno-associated viral vector comprising an abbreviated human RPGR cDNA.
• XLRP X- linked Retinitis Pigmentosa
• RPGR retinitis pigmentosa GTPase regulator
• Retinitis pigmentosa is a leading form of inherited blindness in humans.
• RP Retinitis pigmentosa
• XLRP X-linked RP
• RPGR is one of the most important RP disease genes.
• the present invention is based on the discovery of an abbreviated form of human RPGR that successfully recreates functional RPGR activity, and thus includes methods for treating subjects who have RP caused by mutations in RPGR.
• Subjects who can be treated by the present methods can include those who have loss of visual function (e.g., impaired response on electroretinographic (ERG) testing), but retain some photoreceptor cells as determined by optical coherence tomography (OCT).
• the invention provides methods for treating a human subject who has XLRP or another clinically-defined ophthalmological condition due to a loss-of-function mutation in the gene encoding the retinitis pigmentosa GTPase regulator (RPGR) protein.
• RPGR retinitis pigmentosa GTPase regulator
• the methods include administering to the subject a nucleic acid comprising an adeno-associated viral vector comprising an abbreviated human RPGR cDNA, wherein the abbreviated human RPGR cDNA encodes a protein that is at least 80% identical to the full length of SEQ ID NO:2, optionally with a deletion of up to a total of 200 additional amino acids in the region surrounding the deleted region in SEQ ID NO:2 (i.e., between amino acids 861 and 862 of SEQ ID NO:2).
• the RPGR cDNA is under the control of a human rhodopsin kinase (hRK) promoter, e.g., an hRK promoter that comprises or consists essentially SEQ ID NO:5.
• hRK human rhodopsin kinase
• the adeno-associated viral vector is AAV-2, serotype-8 (AAV2/8) or AAV-8.
• the RPGR cDNA comprises or consists essentially of a sequence that is at least 80% identical to SEQ ID NO: 1.
• the human RPGR cDNA encodes a protein that is at least 95% identical to the full length of SEQ ID NO:2.
• the methods include administering the nucleic acid in a low dose of about 2 x 10 10 vg/mL, a middle dose of about 2 x 10 11 vg/mL, or a high dose of about 2 x 10 12 vg/mL.
• the nucleic acid is administered into the subretinal space.
• a micro injection cannula is inserted into the subretinal space, temporal to the optic nerve and just above the major arcade vessels, so that fluid flow can be directed towards the macula.
• the invention provides nucleic acids encoding an abbreviated human RPGR, wherein the abbreviated human RPGR cDNA encodes a protein that is at least 80% identical to the full length of SEQ ID NO:2, optionally with a deletion of up to 200 additional amino acids surrounding the deleted region of SEQ ID NO:2.
• the RPGR cDNA is under the control of a human rhodopsin kinase (hRK) promoter, e.g., an hRK promoter that comprises or consists essentially SEQ ID NO:5.
• hRK human rhodopsin kinase
• the RPGR cDNA comprises or consists essentially of a sequence that is at least 80% identical to SEQ ID NO: 1.
• the human RPGR cDNA encodes a protein that is at least 95% identical to the full length of SEQ ID NO:2.
• the human RPGR cDNA is at least 80% identical to the full length of SEQ ID NO: l, optionally with a deletion of nucleotides encoding up to 200 additional amino acids surrounding the deleted region.
• vectors e.g., adeno-associated viral vectors, e.g., AAV-2, serotype-8 (AAV2/8) or AAV-8, comprising the nucleic acids encoding an abbreviated human RPGR as described herein, as well as isolated cells (i.e., cells that are not present in a living human subject or host animal) that harbor the nucleic acids encoding an abbreviated human RPGR and optionally express the abbreviated human RPGR protein.
• adeno-associated viral vectors e.g., AAV-2, serotype-8 (AAV2/8) or AAV-8
• isolated cells i.e., cells that are not present in a living human subject or host animal
• FIGS 1A-B Maps of the native human RPGR ORF15 coding region and both shortened forms of AAV-delivered human ORF15cDNA.
• B Immunoblots for the two recombinant forms of human RPGR-ORF15.
• AAV delivery of the small- deletion human cDNA (AAV-ORF15-L, "long form") leads to expression of a human RPGR-ORF15 protein of ⁇ 160 kD in size.
• AAV delivery of the large-deletion human cDNA (AAV-ORF15-S, "short form") leads to expression of a protein of -130 kD in size.
• Both forms of human RPGR-ORF15 protein are smaller than endogenous human RPGR ORF15 found in human retinal tissue ( ⁇ 200 kD).
• FIGS 2A-D RPGR ORF 15 expression in RPGR ⁇ A mouse retinas following subretinal delivery of AAV -RPGR ORF15.
• A Fluorescence images of both the short (ORF15-S) and long (ORF 15- L) forms of human RPGR ORF15 protein expression superimposed on Nomarski images to illustrate the layers of the outer retina. Staining of unfixed frozen retinal sections was performed at 3 weeks following treatment at 1- 2 months of age.
• RPE retinal pigment epithelium
• OS outer segment
• CC connecting cilium (transition zone)
• IS inner segment
• ONL outer nuclear layer.
• the fluorescent signal for the long form of ORF 15 shows very little, if any mislocalization, and is largely limited to the connecting cilium region similar to wt. OS, outer segment; CC (TZ), connecting cilium (transition zone); IS, inner segment; ONL, outer nuclear layer.
• FIG. 3 Immunohistochemical (yellow in original) analyses of rod and cone photoreceptors in treated (short and long form of ORF 15) and control RPGR-/- mouse retinas at age 13 months (6-months post injection).
• ORF 15 short form of ORF 15
• rhodopsin and cone opsin mixed S & M cones in the inferior retina
• mislocalization staining patterns are virtually indistinguishable from those seen in the control retina.
• rod and cone outer segments are shortened and disorganized with a reduced outer nuclear layer compared to an age matched wt retina.
• ORF15 AAV8-ORF15-1
• rhodopsin shows outer segment partitioning similar to WT mouse retina.
• rod outer segments are longer and well organized and the ONL is thicker compared with the control retina.
• Cone opsin staining shows more numerous cone photoreceptors with elongated and well-organized outer segments in the ORF 15 long form treated RPGR-/- mouse retina compared with control.
• FIGS 4A-B Rescue of photoreceptor cells following treatment with RPGR ORF 15-1 in RPGR-/- mice.
• A Shown are stacked bar graphs for ONL thickness (top) and IS/OS length (bottom) for treated (red in original) and fellow control (blue in original) eyes in 3 mice at 18 months of age.
• B Representative light micrographs from a WT mouse and an ORF15-1 treated and fellow control eye from an RPGR-/- mouse at 18 months of age. Images were taken from the mid periphery along the vertical meridian in the superior retina,
• Figures 5A-C (A) Rod a-wave, rod b-wave, and cone b-wave amplitudes from 16 RPGR-/- mice at 11-14 months of age. Control eyes (OD) showed disproportionate loss of cone b-wave amplitude relative to rod b-wave amplitude compared with the lower limits for wild-type mice. Except in one instance, treated eyes (OS) all had larger responses than fellow control eyes In particular, note that more than half of the treated eyes at this age had rod ERG b-wave amplitudes that were at or above the lower limit of wild-type. Mean values for all three measures were significantly different between eyes (P ⁇ 0. 01).
• FIG. 6 Full-field ERGs to 0.5 Hz flashes of white light and to 30 Hz flashes of the same white light from 5 patients with XLRP due to RPGR ORF 15 mutations. Three or more traces are superimposed to illustrate reproducibility. Dots above traces designate flash onset. While the responses to 0.5 Hz responses were reduced by only 6% to 65% below the lower limit of normal (350 ⁇ ), the responses to 30 Hz flashes were nondetectable as illustrated (i.e., without bandpass filtering and signal averaging).
• Viral vector-mediated somatic gene therapy has shown great promise in treating animal models of human retinal degenerative disease.
• AAV adeno-associated virus
• small animal models Ali and others 2000; Pang and others 2012; Pawlyk and others 2010; Pawlyk and others 2005; Tan and others 2009
• large animal models Acland and others 2001 ; Alexander and others 2007; Beltran and others 2012; Komaromy and others 2010; Lheriteau and others 2009.
• the retinal pigment epithelium (RPE) or photoreceptors have been the primary targets for transgene expression.
• LCA Leber Congenital Amaurosis
• Maclaren and others 2014 choroideremia
• the present inventors have previously demonstrated functional and morphological rescue of both rod and cone photoreceptor cells in mice lacking RPGR using an abbreviated murine RPGR ORF15 isoform lacking about 600 bp in the purine-rich carboxyl terminus using a transgenic approach (Hong and others 2005). Some variation in the length of the repetitive region is frequently found in normal individuals (Bader and others 2003; Jacobi and others 2005; Karra and others 2006). However, the function of an abbreviated human RPGR has not been described.
• RPGR is expressed in a complex pattern, with both default and ORF 15 variants having been described (Vervoort and others 2000).
• the default or constitutive form of RPGR spans exons 1-19 and ORF 15 terminates in a large alternative exon designated ORF 15 before the onset of exons 16-19.
• the ORF15 exon is unique in that it contains a long stretch of purine rich repetitive sequence that proved difficult to clone into cDNA and unstable in many procedures of recombinant DNA
• RPGR null mice manifest a slowly progressive retinal degeneration that is characterized by early cone opsin
• RPGR RPGR interacting protein
• the connecting cilium is analogous to the transition zone of motile or primary cilia that may serve as a gateway to the outer segment.
• Isoform A is at Accession No. NM_000328.2 (nucleic acid) and NP_000319.1 (protein); Isoform C is at Accession No. NM_001034853.1 (nucleic acid) and
• Variant (A) uses an alternate splice site and contains multiple alternative exons in the 3' coding region, compared to variant C, and encodes isoform A (also referred to as isoform 1) that is shorter and has a distinct C-terminus, compared to isoform C.
• the sequence used in the exemplary compositions described herein is set forth below as SEQ ID NO: 1.
• the sequences of human RPGR useful in the compositions and methods described herein can be at least 80%, e.g., 85%, 90%, 95%, or 100% identical to the full length of SEQ ID NO: 1, with up to an additional 50, 100, 150, or 200 amino acids deleted from the deleted region, indicated by dashes in the sequence below.
• the comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm.
• the percent identity between two amino acid sequences can determined using the Needleman and Wunsch ((1970) J. Mol. Biol.48:444-453) algorithm which has been incorporated into the GAP program in the GCG software package (available on the world wide web at gcg.com), using the default parameters, e.g., a Blossum 62 scoring matrix with a gap penalty of 12, a gap extend penalty of 4, and a frameshift gap penalty of 5.
• a replacement gene construct is used in which an abbreviated human RPGR cDNA as described herein is placed under the control of a human rhodopsin kinase (hRK) promoter.
• the RK promoter is approx.200 bp in length (a short promoter derived from the rhodopsin kinase (RK) gene, which has been shown to drive cell-specific expression in rods and cones (Khani et al, 2007; Sun et al, 2010; Young et al,
• hRK promoter sequence is -112/+87 (Khani et al., 2007):
• the abbreviated human RPGR cDNA as described above, is packaged into a delivery vector, e.g., an AAV8 or AAV2/8 vector.
• Replacement genes can be administered in any effective carrier, e.g., any formulation or composition capable of effectively delivering the component gene to cells in vivo.
• Approaches include insertion of the gene into non-pathogenic, non- replicating viral vectors, including recombinant retroviruses, adenovirus, adeno- associated virus, lentivirus, and herpes simplex virus- 1, or recombinant bacterial or eukaryotic plasmids.
• Viral vectors transfect cells directly; plasmid DNA can be delivered naked or with the help of, for example, cationic liposomes (lipofectamine) or derivatized (e.g., antibody conjugated), poly lysine conjugates, gramacidin S, artificial viral envelopes or other such intracellular carriers, as well as direct injection of the gene construct or CaPC precipitation carried out in vivo.
• liposomes lipofectamine
• derivatized e.g., antibody conjugated
• poly lysine conjugates e.g., gramacidin S
• artificial viral envelopes e.g., viral envelopes or other such intracellular carriers
• a preferred approach for in vivo introduction of nucleic acid into a cell is by use of a viral vector containing nucleic acid, e.g., a cDNA.
• a viral vector containing nucleic acid e.g., a cDNA.
• Infection of cells with a viral vector has the advantage that a large proportion of the targeted cells can receive the nucleic acid.
• molecules encoded within the viral vector e.g., by a cDNA contained in the viral vector, are expressed efficiently in cells that have taken up viral vector nucleic acid.
• Retrovirus vectors and adeno-associated virus vectors can be used as a recombinant gene delivery system for the transfer of exogenous genes in vivo, particularly into humans. These vectors provide efficient delivery of genes into cells, and the transferred nucleic acids are stably integrated into the chromosomal DNA of the host.
• the development of specialized cell lines (termed "packaging cells") which produce only replication-defective retroviruses has increased the utility of retroviruses for gene therapy, and defective retroviruses are characterized for use in gene transfer for gene therapy purposes (for a review see Miller, Blood 76:271 (1990)).
• a replication defective retrovirus can be packaged into virions, which can be used to infect a target cell through the use of a helper virus by standard techniques. Protocols for producing recombinant retroviruses and for infecting cells in vitro or in vivo with such viruses can be found in Ausubel, et al, eds., Current Protocols in Molecular Biology, Greene Publishing Associates, (1989), Sections 9.10-9.14, and other standard laboratory manuals. Examples of suitable retroviruses include pLJ, pZIP, pWE and pEM which are known to those skilled in the art. Examples of suitable packaging virus lines for preparing both ecotropic and amphotropic retroviral systems include ⁇ , ⁇ , ⁇ 2 and ⁇ .
• Retroviruses have been used to introduce a variety of genes into many different cell types, including epithelial cells, in vitro and/or in vivo (see for example Eglitis, et al. (1985) Science 230: 1395-1398; Danos and Mulligan (1988) Proc. Natl. Acad. Sci. USA 85:6460-6464; Wilson et al. (1988) Proc. Natl. Acad. Sci. USA 85:3014-3018; Armentano et al. (1990) Proc. Natl. Acad. Sci. USA 87:6141-6145; Huber et al. (1991) Proc. Natl. Acad. Sci. USA 88:8039- 8043; Ferry et al. (1991) Proc. Natl. Acad. Sci. USA 88:8377-8381; Chowdhury et al.
• adenovirus -derived vectors The genome of an adenovirus can be manipulated, such that it encodes and expresses a gene product of interest but is inactivated in terms of its ability to replicate in a normal lytic viral life cycle. See, for example, Berkner et al, BioTechniques 6:616 (1988); Rosenfeld et al, Science 252:431-434 (1991); and Rosenfeld et al, Cell 68: 143-155 (1992).
• adenoviral vectors derived from the adenovirus strain Ad type 5 dl324 or other strains of adenovirus are known to those skilled in the art.
• Recombinant adenoviruses can be advantageous in certain circumstances, in that they are not capable of infecting non- dividing cells and can be used to infect a wide variety of cell types, including epithelial cells (Rosenfeld et al, (1992) supra).
• the virus particle is relatively stable and amenable to purification and concentration, and as above, can be modified so as to affect the spectrum of infectivity.
• introduced adenoviral DNA (and foreign DNA contained therein) is not integrated into the genome of a host cell but remains episomal, thereby avoiding potential problems that can occur as a result of insertional mutagenesis in situ, where introduced DNA becomes integrated into the host genome (e.g., retroviral DNA).
• the carrying capacity of the adenoviral genome for foreign DNA is large (up to 8 kilobases) relative to other gene delivery vectors (Berkner et al, supra; Haj-Ahmand and Graham, J. Virol. 57:267 (1986).
• Adeno-associated virus is a naturally occurring defective virus that requires another virus, such as an adenovirus or a herpes virus, as a helper virus for efficient replication and a productive life cycle.
• Adeno-associated virus is a naturally occurring defective virus that requires another virus, such as an adenovirus or a herpes virus, as a helper virus for efficient replication and a productive life cycle.
• AAV vector such as that described in Tratschin et al, Mol. Cell. Biol. 5:3251-3260 (1985) can be used to introduce DNA into cells.
• a variety of nucleic acids have been introduced into different cell types using AAV vectors (see for example Hermonat et al, Proc. Natl. Acad. Sci. USA 81:6466-6470 (1984); Tratschin et al, Mol. Cell. Biol.
• the viral delivery vector is a recombinant AAV2/8 virus.
• Subjects who are candidates for the present methods of treatment include those who have a diagnosis of RP caused by mutations in the gene encoding RPGR.
• Subjects suffering from other ophthalmological clinically-defined conditions caused by mutations in the gene encoding RPGR e.g., X-linked cone-rod dystrophy, can also be treated using the methods described herein.
• a diagnosis of XLRP or another ophthalmological condition caused by mutations in the gene encoding RPGR can be made using methods known in the art.
• the methods described herein can include identifying a subject, e.g., a child, adolescent, or young adult subject, who has XLRP or another ophthalmological condition caused by mutations in the gene encoding RPGR, or who is suspected of having XLRP or another ophthalmological condition caused by mutations in the gene encoding RPGR (e.g., based on the presence of symptoms of the condition and no other obvious cause), and obtaining a sample comprising genomic DNA from the subject, detecting the presence of a mutation in RPGR using known molecular biological methods, and selecting a patient who has a mutation in RPGR that causes XLRP or another condition.
• a subject e.g., a child, adolescent, or young adult subject
• XLRP or another ophthalmological condition caused by mutations in the gene encoding RPGR e.g., based on the presence of symptoms of the condition and no other obvious cause
• Detecting a mutation in RPGR can include detecting a mutation in ORF15, e.g., as described in Sandberg et al, (2007). Invest Ophthalmol Vis Sci 48, 1298-304; Dror et al, Am J Hum Genet. Nov 2003; 73(5): 1131-1146.
• Mutations in RPGR ORF15 include frameshift mutations, nonsense mutations, splice-site mutations, and missesnse mutations.
• Exemplary mutations include ORF15Glu446 (1-bp-del), ORF15Glu447 (2-bp-del), and ORF15GLys521(l- bp-ins).
• Detecting a mutation in RPGR can also include sequencing all or part of (e.g., the ORF 15 region) the RPGR gene in a subject, and comparing the sequence to a reference sequence (e.g., GenBank Accession No. NG_009553.1), to detect a mutation.
• a reference sequence e.g., GenBank Accession No. NG_009553.1
• Frameshift mutations, truncation mutations, mutations that alter a conserved amino acid, or mutations that affect a regulatory (e.g., promoter) region can be considered to be mutations that can cause XLRP or another ophthalmological condition as described herein; an alteration in function can be confirmed by expressing the mutant in vitro (e.g., in cultured cells) or in vivo (e.g., in a transgenic animal), and assaying, e.g., function or subcellular localization.
• Patients with XLRP or another ophthalmological condition due to RPGR mutations that can be treated using a method described herein preferably retain some photoreceptors and visual function, e.g., as measured by standard visual function or field tests and/or Optical Coherence Tomography (OCT, e.g., Spectral Domain-OCT (SD-OCT)); see, e.g., Sandberg et al, Invest Ophthalmol Vis Sci. 2007;48: 1298- 1304.
• OCT Optical Coherence Tomography
• the methods described herein can include identifying subjects who have been diagnosed with XLRP or another ophthalmological condition due to RPGR mutations, who have a confirmed mutation in RPGR that causes their condition, and testing their visual ability and detecting the presence of residual central photoreceptors.
• Subjects e.g., child, adolescent, young adult, or adult subjects, who can be treated using the present methods will preferably have visual acuity of at least 20/200 (methods for determining visual acuity are well known in the art; see, e.g., Johnson, Deafness and Vision Disorders: Anatomy and Physiology, Assessment Procedures, Ocular
• R GR A mice The generation and analysis of R GR A mice have been described previously (Hong and others 2000).
• a second ORF15 cDNA was constructed through recombinant DNA manipulation which contained a 126-codon (378 bp) in-frame deletion within the highly repetitive region of exon 15 (with 3,081 -bp remaining in the ORF 15 exon) (codons 862-988del,"long form"). These ORF15 cDNAs were sequenced to verify fidelity.
• RPGR cDNAs were inserted into the multiple cloning site of the parental pAAV-RK-zsGreen vector. The resulting pAAV-RK-mRPGR and pAAV-RK-hRPGR vectors were packaged into AAV.
• AAV2/8 pseudotyped vector was generated by tripartite transfection: (1) AAV vector plasmid encoding the gene of interest, (2) AAV helper plasmid pLT-RC03 encoding AAV Rep proteins from serotype 2 and Cap proteins from serotype 8, and (3) adenovirus helper miniplasmid pHGTI-Adenol) into 293A cells.
• the transfection was performed using a protocol developed by Xiao and co-workers (Xiao, et al, 1998). Two days after transfection, cells were lysed by repeated freeze and thaw cycles. After initial clearing of cell debris, the nucleic acid component of the virus producer cells was removed by Benzonase treatment.
• the recombinant AAV vector particles were purified by iodixanol density gradient. The purified vector particles were dialyzed extensively against PBS and tittered by dot blot hybridization.
• mice were placed under general anaesthesia with an intraperitoneal injection of ketamine (90 mg/kg)/xylazine (9 mg/kg).
• a 0.5% proparacaine solution was applied to the cornea as a topical anesthetic.
• Pupils were dilated with topical application of cyclopentolate and phenylephrine hydrochloride.
• a small incision was made through the cornea adjacent to the limbus using an 18-gauge needle.
• a 33-gauge blunt needle fitted to a Hamilton syringe was inserted through the incision behind the lens and pushed through the retina. All injections were made subretinally in a location within the nasal quadrant of the retina.
• Injections were made subretinally within the nasal quadrant of the retina. Each eye received either 2 x 10 9 vector genome (AA V- ORF15-L) or 5 x 10 9 vector genome (AA V- ORF15-S) in a 1 ⁇ volume.
• RPGR-ORF15 vectors were administered to the left eye (OS, oculus sinister) and control vector (AA V8-RK- EGFP) were administered to the right eye (OD, oculus dexter). These are referred throughout this text as “treated” or "control”, respectively.
• Visualization during injection was aided by the addition of fluorescein (lOOmg/ml AK-FLUOR, Alcon, Inc.) to the vector suspensions at 0.1% by volume.
• Retinal tissues were homogenized in RIPA buffer, boiled in Laemmli buffer and loaded at 15 ⁇ g/lane on 5% SDS-PAGE gels. After gel separation, proteins were blotted to PVDF membrane by electrotransfer. The membranes were blocked with 5% non-fat milk and incubated with primary antibodies overnight at room temperature. After washing, membranes were incubated with peroxidase-conjugated secondary antibodies. SuperSignal ® West Pico Chemiluminescent Substrate (Pierce) was used for detection. For normalization, protein samples were separated on standard SDS- PAGE and probed with a transducin a antibody (gift of Dr. Heidi Hamm, Vanderbilt University).
• mice were dark-adapted overnight and anesthetized with sodium pentobarbital injected intraperitoneally prior to testing. Both pupils of each animal were topically dilated with phenylephrine hydrochloride and cyclopentolate hydrochloride, and mice were then placed on a heated platform. Rod dominated responses were elicited in the dark with 10- ⁇ 8 flashes of white light (1.37 x 10 5 cd/m 2 ) presented at intervals of 1 minute in a Ganzfeld dome. Light-adapted, cone responses were elicited in the presence of a 41 cd/m 2 rod-desensitizing white background with the same flashes (1.37 x 10 5 cd/m 2 ) presented at intervals of 1 Hz. ERGs were monitored
• amplitudes to that condition ranged from 53 ⁇ to 329 ⁇ OD and from 59 ⁇ to 282 ⁇ OS.
• Their amplitudes to 30 Hz flashes of the same white light, reflecting cone function alone and monitored with bandpass filtering and signal averaging for amplitudes ⁇ 10 ⁇ ranged from 0.98 ⁇ to 23.5 ⁇ OD and from 0.95 ⁇ to 20 ⁇ OS.
• the ratio of response amplitude to 0.5 Hz flashes divided by response amplitude to 30 Hz flashes had a mean ⁇ standard error of 47.0 ⁇ 12.7 OD and 48.7 ⁇ 13.0 OS.
• Example 1 AAV-mediated Expression of human RPGR ORF15
• ORF 15 By western blotting, 2 weeks following AAV vector administration, the long form of ORF 15 produced an approximately 160-kD protein while the short form of ORF 15 produced an approximately 125-kD protein. Both protein products were smaller than native ORF 15 seen in human retinal tissue (approximately 200 kD) (Figs. IB, C). Both forms of replacement ORF15 appeared as a single band when probed with an antibody against the C-terminus of human RPGR. Under our experimental conditions and the dosages given, the expression levels of ORF15-S and ORF 15-L were comparable. Control eyes (right eyes) received AAV-GFP.
• ORF 15 Both forms of ORF 15 could be seen in the retina of R GR 7" mice by immunofluorescence staining of unfixed cryosections (3 weeks following subretinal injections) and correctly localized to the layer in between the inner and outer segments where the connecting cilia reside.
• the short form (AAV8-ORF15- s) gave much weaker signals (Fig. 2A) than the long form (AAV8-ORF15-1).
• the signal from the long form treated retinas appeared indistinguishable from the WT signal (Fig. 2A, B).
• Double-labeling with an antibody for the ciliary rootlets which originate from the proximal ends of basal bodies and extend toward the cell interior and thus serve as an excellent marker for the ciliary region (Hong and others 2003; Yang and others 2002), confirmed the correct subcellular localization of the recombinant RPGR to the connecting cilia (Fig. 2B).
• Fig. 2B Double-labeling with an antibody for the ciliary rootlets, which originate from the proximal ends of basal bodies and extend toward the cell interior and thus serve as an excellent marker for the ciliary region
• Figure 2C shows a bar graph representing RPGR label counts relative to the counts of rooteletin fibers in Rpgr -/- mouse retinas treated with either the long or short form of human ORF 15 as well as in untreated wildtype mouse retinas.
• ORF 15-1 treated eyes were found to have more rod and cone cells (with nearly normal-appearing outer segments) than control or ORF15-S treated eyes.
• Figure 4A illustrates ONL thickness and IS/OS length by region for treated and control eyes in the three mice at 18 months of age.
• Figure 4B shows representative light micrographs taken from a representative ORF 15-L treated and fellow control eye at 18 months of age.
• the best-preserved area has only about 2-3 rows of loosely arranged photoreceptor nuclei with shortened and disorganized photoreceptor inner/outer segments. Note that the margins of the inner and outer segments are no longer distinct.
• the treated retina on the other hand, has about 5-6 rows of photoreceptor cells throughout, with longer, better organized, and distinct inner and outer segments.
• FIG. 5A shows rod and cone ERG amplitudes by eye for 16 mice who were tested between 11 and 14 months of age.
• Control eyes (OD) showed disproportionate loss of cone b-wave amplitude relative to rod b-wave amplitude compared with the lower limits for wild-type mice, as previously observed in this murine model of RPGR _/ ⁇ mice and evidence for a cone- rod degeneration.
• OS treated eye
• OD fellow control eye
• FIG. 5C Representative rod and cone ERGs are shown in Fig. 5C to illustrate waveforms in treated and control eyes, including a WT, at 18 months of age (the final time point).
• Rod function in control eyes at this age is severely reduced (by 75%, on average), while cone function is minimal and in some cases virtually non-detectable.
• treated eyes at this time point still have substantial rod and cone function although below those seen in WT eyes.
• X-linked retinitis pigmentosa RPGR mutations in most families with definite X linkage and clustering of mutations in a short sequence stretch of exon ORF15. Invest Ophthalmol Vis Sci 44, 1458-63.
• RPGR retinitis pigmentosa GTPase regulator
• Retinitis pigmentosa GTPase regulator (RPGR)-interacting protein is stably associated with the photoreceptor ciliary axoneme and anchors RPGR to the connecting cilium. J Biol Chem 276, 12091-12099.
• PAWLYK BS BULGAKOV OV, LIU X, XU X, et al. (2010).
• Replacement gene therapy with a human RPGRIPl sequence slows photoreceptor degeneration in a murine model of Leber congenital amaurosis.
• PAWLYK BS SMITH AJ, BUCH PK, ADAMIAN M, et al. (2005).
• Gene replacement therapy rescues photoreceptor degeneration in a murine model of Leber congenital amaurosis lacking RPGRIP.
• ROEPMAN R BERNOUD-HUBAC N, SCHICK DE, MAUGERI A, et al. (2000).
• the retinitis pigmentosa GTPase regulator (RPGR) interacts with novel transport-like proteins in the outer segments of rod photoreceptors.
• Rd9 is a naturally occurring mouse model of a common form of retinitis pigmentosa caused by mutations in RPGR-ORF15. PLoS One 7, e35865.
• Rootletin a novel coiled-coil protein, is a structural component of the ciliary rootlet. J Cell Biol 159, 431-440.

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